(1) Field of the Invention
This invention relates to a cam mechanism suitable for use in a variety of apparatus which can automatically carry out assembly, machining, feeding, conveyance, ejection and various other operations, and more specifically to a cam mechanism adapted to convert a continuous rotary motion into a compound motion which consists of two linear motions, one being in the horizontal direction and the other in the vertical direction.
(2) Description of the Prior Art
As a cam mechanism which was proposed before by the same applicant and is of the same type as that of this invention, there is a cam mechanism pertaining to the invention disclosed in Japanese Patent Publication No. 4978/1980. In the cam mechanism disclosed in the above-referred to Japanese Patent Publication No. 4978/1980, especially in FIG. 1 of the publication, an input shaft is supported rotatably on a housing, a first and second globoidal cams are fixedly arranged close to each other on the input shaft, each of the globoidal cams is provided with a tapered rib having a predetermined geometrical profile, first and second driven shafts corresponding respectively to the first and second globoidal cams are rotatably supported on the housing in such a way that the driven shafts are perpendicular to the input shaft and are parallel to each other, first and second driven turrets are fixedly attached respectively to the first and second driven shafts, each of the driven turrets is provided on the periphery thereof with a cam follower which holds the tapered rib of its corresponding globoidal cam from both sides thereof, and the first and second driven shafts are fixedly provided with respective arms, whereby to cause an output member to undergo a compound motion consisting of two linear motions.
However, such a cam mechanism is accompanied by such problems as complex structure, size-up, cost-up and the like because use of two globoidal cams is essential and parts are hence increased in number.
These problems become serious particularly when the cam mechanism is used as or incorporated in a base machine for a machine tool adapted to carry out automatically multistep operations such as assembly and/or machining of various works or workpieces. The term "base machine" as used herein means a drive mechanism which constitutes the principal part of an automatic assembly (and/or machining) apparatus adapted to feed and place a variety of works successively at prescribed positions on an intermittently-rotating index table and then to assemble and/or machine the thus-placed works.
Such a base machine generally includes a plurality of pick-and-place units for feeding or ejecting various works to or from the index table. Each of the pick-and-place units is designed in such a way that it undergoes a compound motion consisting in combination of a horizontal linear motion and a vertical linear motion. However, base machines which have publicly been provided are each equipped with a drive source for the index table and additional drive sources respectively for individual pick-and-place units, leading to complexity and size-up of overall systems. These problems may principally be attributed to the complexity and size-up of a mechanism which serves to convert each continuous rotary motion from each drive source to a compound motion and to transmit the compound motion to its corresponding output member, namely, pick-and-place unit. Thus, an attempt to drive both index tables and pick-and-place units by a single drive source resulted in further complexity and size-up because it required the provision of a number of gears and motion convertors.